Method of regulating the supply of molten metal to a casting cavity

ABSTRACT

In a continuous casting machine a rotatable wheel is provided with a circumferential groove in its outwardly directed circumferential edge face. A metal tape covers the groove over a portion of arc and defines therewith a cavity for molten metal. Cooling means cools the wheel and thereby the molten metal in the cavity. Supply means is associated with the wheel and discharges additional molten metal into the cavity below the level of molten metal already contained therein at a rate which is a function of the flow resistance opposed to such discharge by the molten metal in the cavity.

United States Patent Properzi Aug. 29, 1972 [54] METHOD OF REGULATING THE 2,683,294 7/1954 Ennor et al ..164/82 PLY OF MQLTEN METAL T() A 3,326,271 6/1967 Cofer 164/278 CASTING CAVITY 3,331,431 7/1967 Bray et al 164/87 X 3,333,624 8/1967 Cofer et al ..l64/87 1 Inventorl Ilario Propmi, Via Cosimo del 3,333,629 8/1967 Ward ..l64/278 Fame, 10, Milan, Italy Primary ExaminerR. Spencer Annear [22] Ffled' 1970 Attorney-Michael S. Striker [21] Appl. No.: 66,045

[57] ABSTRACT Related US. Application Data In a continuous casting machine a rotatable wheel is DIVISIOII of 5611 705,833, 1968, provided with a circumferential groove in its outabandoned. wardly directed circumferential edge face. A metal tape covers the groove over a portion of arc and [30] Foreign Application Priority Data defines therewith a cavity for molten metal. Cooling means cools the wheel and thereby the molten metal March 15, 1967 Italy 13774 A/67 in the cavity. supply means is associated with the wheel and discharges additional molten metal into the [52] US. Cl. ..164/87 cavity below the level of molten metal already [51] hit. Cl. ..B22d 11/06 tamed therein at a rate Whihh is a f ti f the fl 0f 87, resistance pposed to uch discharge the moltenmetal in the cavity. [56] References Cited 10 Claims, 5 Drawing Figures UNITED STATES PATENTS 2,659,948 11/1953 Properzi ..164/278 METHOD OF REGULATING THE SUPPLY OF MOLTEN METAL TO A CASTING CAVITY CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION The present invention generally relates to continuous metal casting, and more particularly to a method for the continuous casting of metal rods and similar bodies. Still more particularly, the present invention relates to the self-repelation of the molten-metal feed in such a continuous casting method.

An application disclosing a machine of the type with which the present invention may be utilized was filed by me on July 2, 1964 under Ser. No. 379,853. It has since matured into US. Pat. No. 3,346,038.

It is known, generally and also from my aforementioned US. patent, to provide continuous casting machines with a wheel rotatable about its axis and provided in an outwardly directed circumferential edge face with a peripheral groove. This groove is covered along a certain portion of are by a metal tape which closes the corresponding portion of the groove and defines therewith a casting cavity into which molten metal is introduced. This molten metal, upon entering the groove in liquid state at the beginning of the closed portion, leaves it in the shape of a continuous solid bar or rod at the end of the closed portion or casting cavity. To effect solidification of molten metal while it is in the closed portion of the groove, suitable cooling means are provided.

While machines of this type have generally been found satisfactory, they do suffer from a problem for which no fully satisfactory solution has theretofore been found. Specifically, the problem is how to feed molten metal into the casting cavity in such a way as to prevent the overflow of metal, that is to avoid feeding molten metal at an excessively high rate, while at the same time assuring that the metal is fed at a rate adequate to fill the cavity so as to obtain the desired product.

It will be clear that if the metal is overfed, that is if too much molten metal is introduced and some of this is allowed to overflow, the casting wheel may become locked because the overflowing metal will of course solidify and may damage the drive means for the wheel. At the very least such overflow would result in the formation of flashes which could require discontinuation of the operation. Conversely, inadequate feed of molten metal would result in displacement of the free surface of the liquid metal bath along the cooling arc of the metal and the solidification would thus be impaired before the rod moves clear of the wheel at the downstream end of the casting cavity.

While many approaches have been suggested for solving this problem, no satisfactory results have heretofore been achieved to my knowledge. One significant shortcoming of all solutions which had been suggested is the fact that it has always been necessary that the filling level of molten metal in the casting cavity be continuously watched by an operator who must, of course, be ready to take immediate corrective action when required. This, on the other hand, makes it necessary for the operator to be dangerously close to the moving molten metal which, as is well known, is likely to splash and give off sparks as a result of the presence of traces of moisture or of the evolution of gas occlusions in the metal baths.

The present invention thus has for its primary object to overcome the disadvantages known from the prior art and to provide for automatic regulation of the feed of additional molten metal into the casting cavity.

More particularly, the present invention has as one above-enumerated purposes.

SUMMARY OF THE INVENTION In accordance with one feature of my invention I utilize a continuous casting machine having a rotatable casting wheel and a metallic tape. The casting wheel has an outwardly directed circumferential edge face provided with a circumferential groove and the metal tape extends partly around this edge face and covers this groove over a portion of arc to define therewith a cavity which is adapted to receive molten metal. Cooling means is associated with the wheel for cooling and thereby solidifying the molten metal in the cavity. Supply means is provided for molten metal, such supply means being associated with the wheel and in accordance with my invention being operative for discharging additional molten metal into the cavity below the level of molten metal already contained therein, and at a rate which is a function of the flow resistance opposed to such discharge by the molten metal contained in the cavity.

In accordance with my invention, the feed or supply of molten metal is automatically self-regulated by making use of the relationship between the outlet or feeding nozzle in the casting cavity and the initial solidification environment of the metal already contained in the cavity.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partly sectioned diagrammatic elevation of a machine capable of carrying out my invention;

FIG. 2 is a detail view, in section, of a portion of FIG.

FIG. 3 is a section taken on the line IIIIII of FIG. 2;

FIG. 4 is a section taken on the line IV-IV of FIG. 2; and

FIG. 5 is a section taken on the line VV of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The continuous casting machine illustrated in FIG. 1 is capable of carrying out my method and is drawn to facilitate its explanation; this machine corresponds substantially to the machine which is for instance disclosed in my US. Pat. No. 3,346,038 which contains a detailed description of such a machine.

As shown in FIG. 1 the machine essentially comprises a frame which supports a continuous casting wheel 11 which is rotatable in the direction of the arrow 12 via a prime mover which is not illustrated. The wheel 11 is provided along its periphery, or more specifically in its outwardly directed circumferential edge face with a groove or casting cavity 14 of generally polygonal cross-sectional configuration. However, the cross-section of the groove 14 is mentioned by way of example only inasmuch as it does not constitute a part of the present invention.

Along a portion of arc whose opposite ends are identified by the reference numerals 16 and 17, the groove 14 is closed by a continuous metal tape 15 overlying the groove Rotary pulley means of conventional type more specifically discussed in my aforementioned U.S. Pat. No. 3,346,038, are provided for driving the tape 15. Such pulleys are identified with numerals 18 and 19 and are rotatable in the direction of the arrows 20. They are supported by a suitable support, generally identified with reference numeral 21. In the region of the enclosed portion of the groove 14, that is along the portion of are located between upstream portion 16 and downstream portion 17, the wheel 11 is cooled from inside and from outside by means of jets of cooling liquid 22 and 23. How this is accomplished is also described more fully in my aforementioned U.S. Patent, and forms no part of the present invention. The tape 15 is deflected into tight engagement with the peripheral surface of the wheel 11 by a tape presser roller 24 provided at the point 16.

Molten metal is fed into the casting cavity constituted by the enclosed portion of the groove 14 and is conveyed by rotation of the wheel 11 and simultaneously cooled so that it solidifies and issues at the point 17, where the tape uncovers the groove, in form of a rod or wire 25. Molten metal introduced into the casting cavity in the region of the inlet end 16 thereof will form a level 29 in the cavity. As a result of cooling of this molten metal solidification takes place below the level 29, and the manner in which this solidification occurs is characteristic and is shown in FIG. 1 and more clearly still in FIG. 2. It will be seen that solidification begins in the areas of contact with the walls of the groove and the tape 15 so that the metal solidifies in direction inwardly away from the walls. Because of the movement of wheel 1 l in the direction of the arrow 12, coupled with continuous introduction of additional molten metal, the point at which total solidification is reached, that is at which no molten core is present any longer, is located below and downstream of the level 29. This is most clearly evident in FIG. 2 where it will be seen that this characteristic pattern of solidification leaves in the region of the inlet end 16 of the cavity a pool of molten metal which converges substantially conically downwardly of the level 29 and is in effect bounded by a connoidal wrapper or interface 39 of solidified metal, which defines a conical hollow.

The molten metal 26, that is the supply of additional molten metal, is fed from a melting furnace (not shown) in a continuous flow to a crucible or supply vessel 27 and issues therefrom through an outlet duct 28 into the casting chamber so as to maintain the level 29 therein. It will be appreciated that the body of molten metal in supply vessel 27 at any given moment will generally have an uppermost level above the level of the outlet of conduit 28. In accordance with the invention the crucible 27 is fastened to a supporting arm 30 which is movable vertically along an upright guide 31. For this purpose, the supporting arm 30 is provided with a projection which engages in a dove-tail-shaped groove 32 formed in the upright guide 31. The projection of the supporting arm 30 is provided with a screwthreaded perforation (not illustrated) which cooperates with a screw-threaded shaft 33, the latter being provided at its top portion with an integral worm gear 34 which engages a horizontally positioned worm 35. The latter is actuated by an electric motor 36 affixed to the shaft of the worm 35. Thus, by rotating the motor 36 in one or in the opposite direction, the shaft 33 is correspondingly rotated and this results in a raising or lowering of the supporting arm 30 and therefore of the crucible 27 which will thus move towards and away from the wheel 11.

FIG. 1 shows that the crucible 27, which contains the molten metal 26 therein is provided with a manually operable adjusting device comprising a rod 37 which can be manually actuated via a lever 38. The rod 37 is movable into and out of the inlet end of the duct 28 so as to increase or decrease the cross-sectional area of this inlet end and thereby throttle the flow of molten metal into the duct 28 to the extent desired. The outlet end of the duct 28 is located, as evident from FIGS. 1 and 2, below the level 29 of the molten metal 26 contained in the cavity constituted by the groove 14 and the tape 15. Additional molten metal issuing from the outlet end of the conduit 28 follows the path indicated by the arrow 40 in FIG. 2, that is it must issue against the resistance offered to it by the molten metal forming the pool in the casting cavity, and it must rise upwardly in this pool in the direction indicated by the arrow 40.

In use of this apparatus for carrying out my novel method, the motor 36 is actuated whereby the crucible 27 and therefore the outlet of the conduit 28 are preset at a desired height which can be readily determined empirically. It will be appreciated that conduit 28 conveys molten metal under pressure, the pressure in this case being that due to the upper metal part contained in supply vessel 27. A further adjustment is effected, if necessary and desired, via the rod 37. Thereafter, the flow of molten metal 26 from the crucible into the casting cavity will adjust itself automatically in accordance with the central concept of my invention as a function of the flow resistance offered by the mass or pool of molten metal confined within the conical wrapper 39 to the discharge of new molten metal from the outlet end of the conduit 28.

In effect, therefore, it might be said that the method is based on the operation of a type of valve whose adjustable member is constituted by the pool of molten metal defined by the conical wrapper 39. It is clear that any need for movable components contacting the molten metal in the casting cavity is eliminated, and it is further clear that the regulatory action provided is proportional to the variation which is obtained in the filling level and that such variation will invariably elicit a prompt response in terms of changes in the inflow of additional molten metal. It is important to note that, if the filling level is lowered, the same is true also of the conical pool located within the solidified metal wrapper 39, so that the throttled outflow passageway or flow clearance is enlarged. This in turn leads to a raising of the filling level because more additional material can flow out from the conduit 28. A raising of the filling level, on the other hand, tends to raise the position of the solidified portion and results in automatic throttling of the outflow of additional molten metal from the conduit 28.

Generally speaking, the diameter of the casting wheel may range between approximately 140 and 200 centimeters and the length of the portion of conduit 28 which is immersed in the cavity may reach a maximum of -25 centimeters so as to effect positioning of the outflow of the conduit 28 within the pool of molten metal bounded by the wrapper 39. The most convenient throttling weight and flow can of course be obtained empirically in a simple manner and it will be obvious that the length of the immersed portion of the conduit 28 will constitute a function of the inside diameter of the conduit also. As the latter is increased, the length of the immersed portion is decreased if the same throttling of material fiow is to be maintained.

It will be clear that movement of the crucible and/or the conduit 28 may be adjusted not simply in the manner illustrated by way of example, but in other ways as well. This does not, however, in any way affect the operation and the inventive principle herein disclosed.

FIGS. 3 5, which are sections taken on the indicated section lines of FIG. 2, are self-explanatory and require no detailed discussion.

It will be understood that each of the features described above, or two or more together, may also find useful application in other types of applications differing from the types described above.

While the invention has been illustrated and described as embodied in a continuous casting method, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended.

1. A method of regulating the supply of molten metal to a casting cavity, comprising the steps of admitting molten metal at an upstream portion of a travelling casting cavity for solidification and withdrawal therefrom at a downstream portion, so that the molten metal is present in said cavity in the region of said upstream portion in a liquid and a solid phase an interface between which changes its position in dependence upon the rate of supply of molten metal into and the rate of withdrawal of solidified metal from said cavity; positioning an outlet for molten metal within said upstream portion of said cavity in said liquid phase proximal to said interface so as to define therewith a flow clearance having an efiective cross-section which increases and decreases in dependence upon the changes of position of said interface; and admitting additional molten metal into said cavity and liquid phase through said outlet and clearance, whereby the rate supply of such additional molten metal will vary with variations in said fiowpath cross-section, and accordingly in dependence upon said rates of supply and withdrawal.

2. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a supply vessel adapted to contain a supply of molten metal, and the molten metal in said supply vessel having an uppermost level above the level of said outlet; and further comprising the step of varying the vertical distance from said uppermost level to said outlet.

3. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a supply vessel adapted to contain a supply of molten metal, and the molten metal in said supply vessel having an uppermost level above the level of said outlet; and further comprising the step of varying the vertical distance from said uppermost level to said interface.

4. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a supply vessel adapted to contain a supply of molten metal, and the molten metal in said supply vessel having an uppermost level above the level of said outlet, and said liquid phase having an upper boundary surface spaced from said interface and above said outlet; and further comprising the step of varying the vertical distance from said uppermost level to said upper boundary surface.

5. A method as defined in claim 2, said supply vessel being movable in vertical direction, and wherein the step of varying the vertical distance from said uppermost level to said outlet comprises moving said vessel in vertical direction.

6. A method as defined in claim 3, said supply vessel being movable in vertical direction, and wherein the step of varying the vertical distance from said uppermost level to said interface comprises moving said vessel in vertical direction.

7. A method as defined in claim 4, said supply vessel being movable in vertical direction, and wherein the step of varying the vertical distance from said uppermost level to said upper boundary surface comprises moving said vessel in vertical direction.

8. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a source of molten metal, said conduit having an effective cross-sectional area; and further comprising the step of varying the effective cross-sectional area of said conduit.

9. A method as defined in claim 1, said outlet being the outlet of a conduit which conveys molten metal under pressure from a source of molten metal; and further comprising the step of varying the pressure under which said molten metal is conveyed by said conduit.

10. A method as defined in claim 1, said interface comprising a conical surface defining a conical hollow filled with molten metal and projecting into said solid phase, and wherein the step of positioning said outlet proximal to said interface comprises positioning said outlet within said conical hollow. 

1. A method of regulating the supply of molten metal to a casting cavity, comprising the steps of admitting molten metal at an upstream portion of a travelling casting cavity for solidification and withdrawal therefrom at a downstream portion, so that the molten metal is present in said cavity in the region of said upstream portion in a liquid and a solid phase an interface between which changes its position in dependence upon the rate of supply of molten metal into and the rate of withdrawal of solidified metal from said cavity; positioning an outlet for molten metal within said upstream portion of said cavity in said liquid phase proximal to said interface so as to define therewith a flow clearance having an effective crosssection which increases and decreases in dependence upon the changes of position of said interface; and admitting additional molten metal into said cavity and liquid phase through said outlet and clearance, whereby the rate supply of such additional molten metal will vary with variations in said flowpath crosssection, and accordingly in dependence upon said rates of supply and withdrawal.
 2. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a supply vessel adapted to contain a supply of molten metal, and the molten metal in said supply vessel having an uppermost level above the level of said outlet; and further comprising the step of varying the vertical distance from said uppermost level to said outlet.
 3. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a supply vessel adapted to contain a supply of molten metal, and the molten metal in said supply vessel having an uppermost level above the level of said outlet; and further comprising the step of varying the vertical distance from said uppermost level to said interface.
 4. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a supply vessel adapted to contain a supply of molten metal, and the molten metal in said supply vessel having an uppermost level above the level of said outlet, and said liquid phase having an upper boundary surface spaced from said interface and above said outlet; and further comprising the step of varying the vertical distance from said uppermost level to said upper boundary surface.
 5. A method as defined in claim 2, said supply vessel being movable in vertical direction, and wherein the step of varying the vertical distance from said uppermost level to said outlet comprises moving said vessel in vertical direction.
 6. A method as defined in claim 3, said supply vessel being movable in vertical direction, and wherein the step of varying the vertical distance from said uppermost level to said interface comprises moving said vessel in vertical direction.
 7. A method as defined in claim 4, said supply vessel being movable in vertical direction, and wherein The step of varying the vertical distance from said uppermost level to said upper boundary surface comprises moving said vessel in vertical direction.
 8. A method as defined in claim 1, said outlet being the outlet of a conduit which communicates with a source of molten metal, said conduit having an effective cross-sectional area; and further comprising the step of varying the effective cross-sectional area of said conduit.
 9. A method as defined in claim 1, said outlet being the outlet of a conduit which conveys molten metal under pressure from a source of molten metal; and further comprising the step of varying the pressure under which said molten metal is conveyed by said conduit.
 10. A method as defined in claim 1, said interface comprising a conical surface defining a conical hollow filled with molten metal and projecting into said solid phase, and wherein the step of positioning said outlet proximal to said interface comprises positioning said outlet within said conical hollow. 